San Francisco: Two military F-15 jets were scrambled late on Friday after a "suicidal" airline worker stole and later crashed an empty passenger plane from the Seattle-Tacoma airport, local officials said.

Local authorities quickly ruled out terrorism as a motive for the incident, and said the F-15s "were not involved in the crash."

An airline employee "conducted an unauthorised takeoff" of an airplane carrying no passengers at the major airport in the northwestern US state of Washington, airport officials said on Twitter.

The aircraft "crashed in south Puget Sound," Sea-Tac Airport said, adding that normal operations at the transport hub had resumed after a pause.

"This is not a terrorist incident. Confirmed info... this is a single suicide male. We know who he is. No others involved," the Pierce County Sheriff said.

The suspect was identified as a 29-year-old Pierce county resident who "acted alone," the sheriff's office added, confirming that there were "no passengers on the plane" when it crashed.

Video taken by a bystander showed the airplane making a loop, then flying low over a body of water.

Alaska Airlines on Twitter said the airplane was a turboprop Q400 airplane belonging to its sister carrier Horizon Air.

Local media described the man who stole the plane as a mechanic.

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Law enforcement officials stand at a staging area, at the ferry terminal in Washington, near a plane crash. Image Credit: AP
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Law enforcement vehicles are shown at the ferry terminal in Steilacoom, Washington, near where a Coast Guard spokeswoman said the agency was responding to a report of a smoke plume and plane crash. Image Credit: AP
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